Well, critical success gives you some bonus above and beyond a normal success, so what else is a critical parry going to do for you beyond blocking your opponent's
strike?

Transcript

GM: The force fields deactivate for two rounds.[SFX]: Whoom!Qui-Gon: Attack! I use the spin-thrust manoeuvre! 14![SFX]: Krrzrzrkk!Obi-Wan: No! Wait! Listen to him!Qui-Gon: Reverse parry! Critical![SFX]: Whoom!GM: A critical parry, huh?Qui-Gon: Yeah, he hits himself!GM: Let me just look that up...Obi-Wan: Do I make it past the force fields?GM: It's eighteen hexes. See if you're fast enough.Obi-Wan: Ah. I don't think I make it.GM: The last force field cuts you off from the fight.Qui-Gon: You and me, bounty hunter! Bring it on![SFX]: Whoom! Whoom!GM: He rolls a critical pirouette.[SFX]: Krrzrzrkk!Qui-Gon: Oooh! I'm learning that when I level up!